Phototoxic retinopathy due to light from the operating microscope has been reported during cataract surgery, as well as during vitreous surgery. A neutral density filter for the coaxial light or coverage of the cornea with various materials has been advocated to prevent retinal complications. However, it is difficult to actually monitor the fundus during surgery with usual methods. The author used an endoscope to demonstrate how intensively the light from the operating microscope is focused on the retinal surface during vitreous surgery.
[Show abstract][Hide abstract] ABSTRACT: This dissertation documents the development of a new illumination
technique for use in the studies of retinal oximetry and fundus
spectroscopy. Intravitreal illumination is a technique where the back of
the eye is illuminated trans-sclerally using a scanning monochromator
coupled into a fiber optic illuminator. Retinal oximetry is the process
of measuring the oxygen saturation of blood contained in retinal vessels
by quantitative measurement of the characteristic color shift seen as
blood oxygen saturation changes from oxygenated blood (reddish) to
deoxygenated blood (bluish). Retinal oximetry was first attempted in
1963 but due to a variety of problems with accuracy and difficulty of
measurement, has not matured to the point of clinical acceptability or
commercial viability. Accurate retinal oximetry relies in part on an
adequate understanding of the spectral reflectance characteristics of
the fundus. The use of intravitreal illumination allows new
investigations into the spectral reflectance properties of the fundus.
The results of much research in fundus reflectance and retinal oximetry
is detailed in this document, providing new insight into both of these
related fields of study. Intravitreal illumination has been used to
study retinal vessel oximetry and fundus reflectometry resulting in
several important findings that are presented in this document. Studies
on enucleated swine eyes have provided new insight into the
bidirectional reflectance distribution function of the fundus. Research
on live swine has shown accurate measurement of retinal vessel oxygen
saturation and provided the first in vivo spectral transmittance
measurement of the sensory retina. A secondary discovery during this
research suggests that vitrectomy alters the retinal vasculature, an
finding that should spawn new research in its own right.
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